Exhaust manifold for supercharged engine

[itiejim]

I'm going to need a new manifold for my supercharged K series engine and have been looking into options.
I cobbled together the previous one, (4-2-1), but with a centrifugal SC in the way it's a bit tighter now and I was looking at using a reputable specialist, hoping that they'd be able to tune it properly to get the most out of the engine.
However, the information I can find on the net seems to indicate that, with a supercharger, a 'tuned' manifold is a waste of time and that effectively you just need to make sure that the system is sufficiently sized to not be restrictive.
This doesn't sound quite right to me, effectively the pulses remain the same, even if the volume of charge has increased- can anyone share some knowledge?
Finally, can anyone advise on how much I should increase pipe diameter to accommodate the extra gasses created by forced induction - presumably ideal primary and secondary lengths don't change?
If I can establish enough information I'm tempted to have a go at making it myself...

[Butter Face]

I had the same conversation with the tuner about my supercharged EP3, he said the same, no point messing with a fancy manifold z I have decayed for the sake of it but I am running the standard (I think 2 inch) which hasn't caused any problems just yet (320bhp)

I don't want a loud car so keeping the standard system suits me fine.

Edited by Butter Face on Thursday 26th January 21:39

[stevieturbo]

itiejim said:

I'm going to need a new manifold for my supercharged K series engine and have been looking into options.
I cobbled together the previous one, (4-2-1), but with a centrifugal SC in the way it's a bit tighter now and I was looking at using a reputable specialist, hoping that they'd be able to tune it properly to get the most out of the engine.
However, the information I can find on the net seems to indicate that, with a supercharger, a 'tuned' manifold is a waste of time and that effectively you just need to make sure that the system is sufficiently sized to not be restrictive.
This doesn't sound quite right to me, effectively the pulses remain the same, even if the volume of charge has increased- can anyone share some knowledge?
Finally, can anyone advise on how much I should increase pipe diameter to accommodate the extra gasses created by forced induction - presumably ideal primary and secondary lengths don't change?
If I can establish enough information I'm tempted to have a go at making it myself...

And as all these threads go...is he really going to build dozens of designs and dyno test them to see what works best for your specific engine ?

I really doubt it given the huge sums of money that would take.

And what sort of power are you hoping to make, and what sort of power are others making with xyz design of exhaust ?

[itiejim]

Stevie, I'm not sure whether you wanted to quote me or Butter Face.

I'm hoping to make 240 BHP. I would have based my exhaust design around the guidance given by Dave Andrews who, it seems, has been involved in plenty of testing of (Rover) K series engines, however, what I'm trying to establish is:

A. How should this be adapted if running around 10psi boost.
B. Is the assertion that exhaust design is far less critical on a forced induction engine just twaddle or true?!

[227bhp]

You design the exhaust of a SC engine just the same as an N/A.
That's a well trodden path, so you should be able to get some dimensions easily enough.

[GreenV8S]

I suspect the optimal cam for the supercharged engine might be quite different to N/A or turbocharged because the supercharger will give you a substantial pressure difference across the engine - figuring that out might be more important than fine tuning the exhaust.

[CrutyRammers]

itiejim said:

However, the information I can find on the net seems to indicate that, with a supercharger, a 'tuned' manifold is a waste of time and that effectively you just need to make sure that the system is sufficiently sized to not be restrictive.

Not an expert by any means, but I'd have thought that's true for a turbocharged engine, rather than a supercharged one, as you say.
(Yes I know a turbo is a type of supercharger for the pedants out there )

[itiejim]

Thanks folks. I'm going to continue running the VVC cams I think. Turbo Technics seemed to get them to work OK and I'm keen to keep the drivability of they offer.
I too follow the logic for a turbocharged engine, but also think that a supercharged one should be properly tuned.
Whilst I can find equations to establish pipe sizes and lengths for NA engines what I can't see is how these should change with boost. Surely it should be possible to establish NA dimensions and then use a factor per psi of boost for supercharged applications?

[Allan L]

CrutyRammers said:

itiejim said:

However, the information I can find on the net seems to indicate that, with a supercharger, a 'tuned' manifold is a waste of time and that effectively you just need to make sure that the system is sufficiently sized to not be restrictive.

Not an expert by any means, but I'd have thought that's true for a turbocharged engine, rather than a supercharged one, as you say.
(Yes I know a turbo is a type of supercharger for the pedants out there )

It isn't pedantic to point out that the exhaust arrangements are complicated by a turbo-supercharger but not with a mechanically driven one.
Not being restrictive applies to the inlet arrangements and the valve timing can indeed be optimised differently for supercharging. In some circles great store is set by high inlet manifold pressure, but in my view that just shows that the inlet valves are not open wide enough or long enough, so are "in the way".

[GreenV8S]

Allan L said:

In some circles great store is set by high inlet manifold pressure, but in my view that just shows that the inlet valves are not open wide enough or long enough, so are "in the way".

One man's boost is another man's backpressure/resistance. The amount of charge in the cylinder is what really matters.

[Jack_and_MLE]

sorry for the hijack

Quick question about your engine, can you give some details?
I was hopping to be able to supercharged my Caterham 21 VVC.

Cheers

Jack

[itiejim]

Jack - I've sent you a PM.

[Evoluzione]

itiejim said:

Whilst I can find equations to establish pipe sizes and lengths for NA engines what I can't see is how these should change with boost. Surely it should be possible to establish NA dimensions and then use a factor per psi of boost for supercharged applications?

That's because nothing changes from Supercharged to N/A as far as the exhaust is concerned.

[itiejim]

Evoluzione said:

That's because nothing changes from Supercharged to N/A as far as the exhaust is concerned.

Ahh, that's interesting, thanks. So even though I'm pushing out more combustion gasses this doesn't change the calculation?

[stevieturbo]

itiejim said:

Ahh, that's interesting, thanks. So even though I'm pushing out more combustion gasses this doesn't change the calculation?

I guess that depends what the calculation is.

[AW111]

Tuned lengths are based on speed of sound through the exhaust, which depends on temperature and pressure, so supercharging shouldn't make a significant difference.
Pipe diameters are based on gas speed, so I would assume the bore should be increased due to the higher gas flow.
At 10 psi, you are using about 70% more air / fuel.

ETA added pressure to 1st sentance.

Edited by AW111 on Sunday 29th January 03:45

[itiejim]

AW111 said:

Tuned lengths are based on speed of sound through the exhaust, which depends on temperature, so supercharging shouldn't make a significant difference.
Pipe diameters are based on gas speed, so I would assume the bore should be increased due to the higher gas flow.
At 10 psi, you are using about 70% more air / fuel.

That's very useful, thanks.